In exterior door assembly designs, the threat of water penetration is the greatest at the bottom of the door. Accordingly, to increase watertightness, the design of the sill threshold is crucial. Commonly used threshold designs, such as a flat sill, a fixed or adjustable threshold on an inclined sill approach, or a “dam” type threshold equipped with weep holes with an adjustable sweep, all manage water drainage, but may still allow some water infiltration. According to some new regulatory standards, the water penetration resistance test will be a primary source of concern because a minute water penetration on the interior of the door could result in a door sill assembly not meeting the standards.
There are other threshold designs, such as a “water retention sill”, that feature a water retention structure at the sill portion, and a relatively high threshold, but such a configuration may not be suitable for using as an entrance door. Other components that contribute to the overall performance of the door system include sweep, pads (dust-plugs), weatherstrip, astragals, and the material of the door itself.